Effectiveness of water-bearing and anti-stripping additives in warm mix asphalt technology

Effects of varying dosages of a water-bearing warm mix asphalt (WMA) additive, Advera®, on a performance grade (PG) binder, PG 64-22, were evaluated. The effectiveness of an amine-based liquid anti-stripping (AS) agent, AD-here® HP Plus, on the Advera®-modified binder was also studied. Furthermore, the effect of reduced oxidative ageing on Advera®-modified binder was investigated. The optimum dosage of Advera® was found to be 6% (by the mass of the binder), which did not alter the base binder's PG. A fairly small amount (0.5%) of the AS agent was found to be effective in increasing the fatigue and low temperature resistances of the Advera®-modified binder. A notable reduction in the high PG temperature was observed when the Advera®-modified binder was aged (short term) at 135°C, and this observation is in agreement with the test results of the Advera® mix, which showed excessive rutting and moisture susceptibility. Test data from a rotational viscometer showed no reduction in the viscosity and the production temperature of the Advera® mix thereof, indicating the need of an alternate laboratory test method to simulate the working mechanism of Advera®. The findings of this study are expected to enhance the inventory of rheological database and help in implementing WMA mixes in Oklahoma and elsewhere.